More likely they are smart enough to understand the impact of a campaign to them, and to him. You become villains for a huge amount of people to despise, and cheer against. Your privacy is annihilated. They dig up every bad thing you did or said, not just the candidate, but everyone close to him, and also the people close to them. They scrutinize your finances. They scrutinize your past conduct. A crowdsourced mob passionately pours through your biography and your past with a fine-toothed comb looking for anything to weaponize against you.
The more you succeed, the higher you rise, proportionally the greater this scrutiny and hatred becomes, and the longer it endures. If you rise high enough, if you do enough on behalf of your supporters, you eventually reach a point where it lasts forever. You can never go out in public without someone shouting "Fuck you!", or harassing you.
It's a Faustian bargain like celebrity, but instead of money or the love of strangers, the only meaningful compensation that is guaranteed is power. So if the President is largely some bureaucratic figurehead...holy shit, why would anyone do it?